Technical Field
The present disclosure generally relates to miniature gas sensors, and in particular to chemireactive gas sensor modules integrated with microelectronic circuits in a single package.
Description of the Related Art
Miniature solid state gas sensors integrated with microelectronics allow construction of an “electronic nose” that can selectively detect the presence of various gases in a wide variety of applications. For example, such sensors can be used to detect toxic substances such as carbon monoxide (CO), methane (CH3), or hydrogen gas (H2) in a home or industrial environment. In another application, ethanol sensors can be provided within portable breathalyzers for use by law enforcement officers.
Chemireactive sensor materials for integration with microelectronics can be provided in various forms, including solids, liquids, gels, aerosols, gases, and the like. One example of a chemireactive material for use in microelectronic gas sensors is a solid electrolyte made of a zirconia-based mixture. Such solid electrolytes are used, for example, in automobile fuel control systems to sense the mixture of exhaust gases, in particular, oxygen, and then to adjust the air-to-fuel ratio to optimize combustion as described in U.S. Pat. No. 6,562,747. In response to a chemical reaction, electrolytic sensor compounds experience a change in conductivity that can be sensed by an electrode and transmitted as an electric current signal. Other types of electrolytes, for example, liquids or gels, can be incorporated into microelectronic gas sensors to measure an amount of a gas that is dissolved into a bodily fluid, e.g., oxygen dissolved in blood, as described in U.S. Pat. No. 5,344,545.